The invention relates to a device and method useful for preventing water from flowing past a closed valve in a pipeline. More specifically, the invention is directed to a sealer member, constructed of a water-swellable material, that is seated on the closure member of the valve to prevent water from leaking past the valve.
Large heat exchangers, of the shell and tube type, are part of the equipment used in many electrical power stations, and other industrial facilities. In these exchangers, it is common practice to use water as a cooling medium. The cooling water enters the exchanger through a large pipeline (for example, 48 inches in diameter) that connects into the floor of an inlet plenum. After passing through the tubes, the water leaves the exchanger through an outlet plenum and another similar pipeline in the plenum floor.
A protective metal grid is welded into both the inlet and outlet pipelines at the point where the pipelines are connected into the plenum floor. The space between the bars which form the grid is only about 12 inches. Butterfly valves are installed in each pipeline from about 24 to 60 inches below the protective grid, and these valves can be closed to isolate the heat exchanger from the cooling water supply. Periodically, scale deposits that form in the tubes must be removed. In this operation, the butterfly valves are closed, chemical cleaning agents are added to the water in the tube side of the exchanger, and the solution is circulated through the tubes, using a pump and lines external to the exchanger (not shown), to remove the scale.
A major problem with this procedure is that a substantial amount of the liquid leaks past the butterfly valves. The result is loss of the cleaning solution to the drain through the outlet plenum, and dilution of the solution from ingress of water through the inlet valve. To counter this effect, the active constituents of the solution must be replenished to maintain the solution at its desired strength inside the exchanger. If the outlet valve was sealed, and the exchanger was closed during the cleaning operation, no water could enter through the inlet valve, since it could not pass through to the drain. The gases generated by the cleaning process, mostly carbon dioxide, would be vented to the atmosphere, as needed, to prevent pressure build up in the exchanger.
Attempts to prevent the butterfly valves from leaking have not been successful, because it's extremely difficult to gain access to the valves. For example, the only way to get inside either of the plenums is through a manway that is 24 inches in diameter. And from either plenum the only access to the valve is through the narrow openings in the non-removable grid above each valve. In addition, no suitable device has been available that could be used to alleviate this problem.